1. Technical Field of the Invention
The present invention relates generally to a disk drive system and, more particularly, to a driver circuit for a voice coil motor in a disk drive system.
2. Description of the Related Art
Conventional magnetic storage devices generally include a magnetic transducer head suspended in close proximity to a recording medium, such as a magnetic disk having a plurality of concentric tracks. The storage device also includes a spindle motor for rotating the disk and a head stack assembly that can include one or more read/write heads. The head stack assembly is controllably positioned over the magnetic disk by an actuator or a servo system in order to read or write information from or to particular tracks on the disk. A head is supported by a flexible suspension or carriage.
The carriage is controllably positioned by an actuator using a voice coil motor (VCM) so that the head can be properly positioned over a particular track on the magnetic disk to perform reading and the like of the magnetic information of the magnetic disk. When the rotation of the magnetic disk is stopped or the reading and the like of the magnetic information is not performed, the magnetic head is retracted to the xe2x80x9cparking zonexe2x80x9d of the magnetic disk. Understandably, such drives may be relatively sensitive to shocks occasioned by mishandling, excessive vibrations, drops and other events causing a rapid acceleration of the disk drive. Should the head crash into a spinning disk because of a rotational shock, for example, debris may be generated which may lead to read or write errors or may result in hard disk drive failure.
In an effort to mitigate the effects of such shocks, a number of latches have been developed to latch the head stack assembly and prevent the heads from contacting the disks. The operative mechanism of such latches are generally electromechanical or magnetic in nature. The function of a latch is typically to prevent the heads of the head stack assembly from leaving the parking zone on the disk during shock events that might otherwise jolt the heads from the parking zone and onto the data-carrying portion of the disk during nonoperative conditions of the drive. However, existing latches suffer from a number of disadvantages.
Generally, electromechanical and magnetic latches are used to attract and latch the head stack assembly when the drive is not in operation. Moreover, to ensure adequate shock protection, the latching force (the force with which the latch holds the head stack assembly to the permanent or electromagnet) must be sufficiently strong. A high magnitude latching force requires a correspondingly high de-latching force to free the head stack assembly. The stronger the magnet, however, the greater the current is necessary to de-latch the head stack assembly when the drive is called into active operation. In turn, such large de-latching current requires a higher capacity voltage supply. For integrated circuits, this de-latching requirement is generally larger than the supply voltage of the integrated circuit.
Therefore, it would be advantageous to provide a circuit to generate and regulate an output voltage sufficient to enable de-latching in which the output voltage is greater than the nominal supply voltage.
The present invention achieves technical advantages as an apparatus and system supplying a regulated voltage to a voice coil motor in a hard disk drive system in which the voltage is of sufficient magnitude to enable de-latching of a head carriage from a latching device. In at least one embodiment, providing a voltage source for the voice coil motor includes a regulator having an input for receiving a first voltage potential and operably configured to provide a second voltage potential to an output selectively coupled to the voice coil motor by a switch. A current source is operably configured to provide a predetermined limited current via a pass transistor associated with the regulator is also included. Further included is a capacitor coupled to the regulator output and operably configured for charging by the current source via the current limited pass transistor.